The Hero and the Crown by Robin McKinleyPublication Date: 2014
Aerin is an outcast in her own father's court, daughter of the foreign woman who, it was rumored, was a witch, and enchanted the king to marry her. She makes friends with her father's lame, retired warhorse, Talat, and discovers an old, overlooked, and dangerously imprecise recipe for dragon-fire-proof ointment in a dusty corner of her father's library. Two years, many canter circles to the left to strengthen Talat's weak leg, and many burnt twigs (and a few fingers) secretly experimenting with the ointment recipe later, Aerin is present when someone comes from an outlying village to report a marauding dragon to the king. Aerin slips off alone to fetch her horse, her sword, and her fireproof ointment.